A pallet is a horizontal portable platform device used as a base for assembling, storage, handling and transporting in a unit load. Pallet structures must be made of hard durable materials constructed to bear high compressive loads over long periods of time, repeated rough usage and high intensity impacts during handling. As a result, wooden pallets for heavy load requirements may weigh as much as 60 to 90 pounds dry and up to 120 pounds wet for 42.times.48 oak pallets. Wooden pallets also suffer disadvantages in that nails work loose, the pallet skews, unbalancing loads, sometimes digging into boxes on the side of the tilt. Or, decking surface members may break, digging and gouging a load material. More recently developed plastic pallets manufactured by conventional molding techniques, such as compression molding, injection molding and vacuum molding afford the strength at somewhat reduced weights but only at greatly increased cost. Similarly, materials such as fiberglass and honeycomb which have also been applied in pallet structures are expensive in material and labor, disproportionately increasing the pallet cost. Conventional paperboard and corrugated board pallets of the disposable type are limited in the compressive strength limits of the paper material that is used, however it is structured.
Another disadvantage of lumber and wood pallets and pallets of wood and paper products is that such materials are hygroscopic, susceptible to changes in moisture content with changes in ambient humidity and wetness. The intrinsic strength of such wood and paper products materials varies with degree of moisture content.
Similarly wood and paper products for use in pallets are normally susceptible to attack and rot by bacteria, fungi, nematodes, etc. In addition, they provide environments which may harbor and support viruses and other human pathogens and pyrogens. It is difficult if not impossible to sterilize, steam clean, or otherwise decontaminate pallets made of such materials for reuse in handling food for human consumption.
It is therefore an object of the present invention to provide a new and improved lightweight, low-cost material structural system and method of constructing same which affords the desired characteristics of toughness, rigidity, hardness, high impact, high compressive strength, and durability in rough handling suitable for use in pallets, industrial platforms and in many other load bearing applications such as building materials in floors, walls, ceilings, etc.
Another object of the invention is to provide a structural system which can be formed from commonly available low-cost paper, paperboard, or other fibrous material and plastic materials combined in interpenetrating network composites to give the desired impact and compressive strength characteristics.
A further object of the invention is to provide new cellular lattice arrangements for structural systems using conventionally available separators for packaging partitions, and separators for packaging elements of the type produced by the paper box manufacturing industry and to new methods and weldments for such partition intersections to rigidify and strengthen partition lattices.
It is also the purpose of this invention to provide structural systems and methods for pallets and other load bearing applications of new material composites impervious to moisture and wetness and with intrinsic strength independent of ambient humidity and wetness. Similarly, such composite materials and structural systems in contemplation of the present invention will be resistant to attack or rot from microorganisms and be non-porous to prevent harboring pathogens, pyrogens, etc.